1. Field of the Invention
This invention relates to a gear shift control apparatus of a vehicle that executes gear shift control of an automatic transmission and, in particular, relates to technology for executing a gear shift of the automatic transmission using a gear shift model.
2. Description of Related Art
Automatic transmissions having a plurality of engaging devices which transmit rotation and torque between an input shaft that receives power from a drive power source and an output shaft that transmits the power to a drive wheel and executing a gear shift by switching between engagement and release of the engaging devices are available. Generally, with such an automatic transmission, adaptation of a demanded value (in other words, a control operation amount) of an operated element (for example, torque) is performed on a control object for each gear stage while performing evaluation on an actual vehicle, and a gear shift is executed based on the adaptation result using a control operation amount determined from a control map obtained in advance for each gear stage. However, as the number of shift stages in automatic transmissions increase, significantly greater effort is required by such adaptation work and, as a result, it is becoming difficult to adopt modes of gear shift control that are based on a control map. Therefore, gear shift model control that is a mode of gear shift control based on a motion equation of each rotating element constituting an automatic transmission is proposed. With such gear shift model control, a control operation amount is uniquely determined by solving a motion equation obtained in advance based on a variation mode (a gear shift target value) that is desirably realized as a result of a gear shift and the determined control operation amount is used to execute a gear shift. For example, Japanese Patent Application Publication No. 2000-97325 (JP 2000-97325 A) describes, with respect to inertia phase control, a technique for executing a gear shift by setting a target value of an input shaft rotation speed of a transmission as a gear shift target value and calculating a demanded value of an engaging-side clutch torque as a control operation amount, and a technique for executing a gear shift by setting respective target values of an input shaft rotation speed and an output shaft torque of a transmission as gear shift target values and calculating a demanded value of an engaging-side clutch torque and a demanded value of a releasing-side clutch torque as control operation amounts using a gear shift model.